It has been recognized that physically infirm persons or persons having certain physical disabilities experience substantial difficulty in moving between standing and seated positions. Movement from either position to the other requires substantial physical muscular exertion as a consequence of the person's weight and the physical mechanics of a person's skeletal construction so as to effect swinging movement of body members at the hip and knee joints.
This problem, associated with moving between standing and seated positions, has been considered in particular with respect to toilets. Illustrative of apparatus specifically designed for the purpose of alleviating the problem through reducing the muscular effort that would otherwise be required is a structure disclosed in U.S. Pat. No. 4,185,335 granted Jan. 29, 1982 to Robert L. Alvis for an invention titled MOVABLE TOILET SEAT ASSEMBLY. Also illustrative of such apparatus are the structures disclosed in U.S. Pat. No. 3,458,872 granted Aug. 5, 1969 to N. E. Hellstrom and U.S. Pat. No. 3,473,174 granted Oct. 21, 1969 to George Cool. Each of the patents disclose a mechanical assembly designed to be associated with a typical toilet bowl and include a mechanical actuator coupled with the seat for effecting its forward pivotable movement between the selected positions. In each of these illustrative seat assemblies, the mechanical actuator comprises a pair of cylinder and piston units operated by pressurized hydraulic fluid. Each of these seat assemblies function to provide support for a person in moving between seated and standing positions and reduce the physical force that must be exerted by the person.
In the structure disclosed by Cool in his patent, the pressurized fluid is obtained from an electric motor driven hydraulic pump that is incorporated in the system. The disadvantage of an apparatus utilizing electrical power for actuation of apparatus in association with a toilet is recognized by Alvis who specifically points out in his patent the hazards of electrical power in an environment where there is water. Thus, Alvis follows the suggestion of Hellstrom and utilizes the pressurized water system which is also used for operation of the toilet. While the typical water source that supplies water for the toilet operation is a convenient source of pressurized fluid for operation of the lifting mechanisms, each of the Alvis and Hellstrom seat assemblies have a same common mechanical limitation which adversely affects their respective capabilities to perform the intended functions. Water supply systems usually provided in either urban or rural areas are of a relatively low pressure type with the water pressure usually being in the range of 30-60 psi. Cylinder and piston mechanisms capable of providing the necessary mechanical force are relatively expensive components and are selected for economic reasons with the smallest possible size being used in any particular application. Selection of such components is demonstrated in the apparatus shown in either of the Alvis and Hellstrom patents. However, recognizing the differences that may be encountered in the fluid pressures that may be encountered in different water supply systems, it will be readily seen that an apparatus which is designed for operation with water pressures in the upper regions of the indicated wide range will not necessarily work with a water supply system that has a pressure at the lower end of that range. Consequently, it is necessary with such systems to take into consideration the variations in fluid pressures and if a universal seat apparatus is to be designed, and the cylinder and piston units must be selected to provide sufficient force when operating with the lowest of the water pressure that may be encountered. Designing of the system with that criteria then results in selecting larger cylinder and pison units to obtain the necessary operating surface area so as to develop the required mechanical force with the lowest of the water pressures. This means that an apparatus which operates with the lowest pressures expected to be encountered is necessarily more expensive than would otherwise be required where higher pressure water supply systems are available.
The power lift toilet seat assemblies illustrated by each of the Hellstrom, Alvis and Cool patents employ a design in assembly of components which requires a greater force be supplied to effect operation as a consequence of a mechanical force disadvantage that is inherent in such illustrated structures. The cylinder and piston actuators in each instance are interconnected between structural members of the assembly such that the effective moment arm of the force applied by the cylinder and piston unit is substantially less than the moment arm that is associated with the weight of the person utilizing the seat and in particular when the seat is at or more closely adjacent to a horizontal position. When this mechanical disadvantage is coupled with the available water pressure limitation, the mechanical limitations of such assemblies are compounded.